Mechanical and transport properties of 10 years old concretes prepared with different coarse aggregates

摘要

Many studies have discussed the effects of coarse aggregate on the mechanical properties of concrete, but this is not the case of the transport properties. The evaluation of the behavior of old concretes becomes of interest as the presence of microcracks can modify its response. Concretes prepared with different coarse aggregates (granitic and quartzitic crushed stone and river gravel, maximum sizes 19 and 38 mm) damaged by drying shrinkage after the exposure during 10 years to moderate environmental conditions are studied. To analyze greater levels of damage the residual properties of the same concretes after high temperature exposure or load-induced cracking are also studied. The paper includes the evaluation of mechanical and transport properties together with a characterization of the internal structure of concrete (density of cracks, density and perimeter of coarse aggregates). The compressive strength decreased after 10 years exposed to laboratory ambient; the concrete prepared with river gravel 38 mm maximum size showed the largest reductions while concretes prepared with quartzitic stone maintained the initial strength level. The different damage processes affect the transport properties in different manner according to the distribution and density of induced cracks; water permeability seems to be the mechanism most sensitive to the type and size of coarse aggregate.